Method for winding strips on the tire building machine

ABSTRACT

A strip member is wound by a tire building machine having a building drum for taking up a strip member of predetermined length without discrete ends and a transfer conveyor for feeding the strip member to the building drum. The winding-start end of the strip member transferred from the transfer conveyor to the building drum and the winding-finish end of the strip member are detected by means of end sensors, measuring the angle through which the building drum has rotated from the output of a winding start signal to the output of a winding finish signal in response to output signals from the sensors by means of an angle detector. A lapping margin between the winding start end and the winding finish end of the strip member is calculated based on the rotational angle and diameter of the building drum by means of an operational means.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The inventions disclosed in this application relate to methodsfor winding an automotive tire building strip member on a building drum.

[0003] More particularly, the first invention in this applicationprovides a method for winding a strip member such as rubberized-steelcord, tread rubber or the like precut to the circumferential length ofthe building drum of a tire building machine on said building drum insuch a manner that both ends of the strip-member will be exactly abuttedagainst each other on the drum.

[0004] The second invention in this application relates to an automotivetire building device wherein the lapping margin of ends of a stripmember wound on its building drum can be automatically measured.

[0005] 2. Prior Art

[0006] In winding a tire strip member on a building drum, it is at timesrequired to insure exact abutment of its ends and at other timesrequired that the lapping margin (positive and negative) be withincertain allowable limits.

[0007] As a technology for insuring exact abutment of both ends of astrip member such as rubberized steel cord or tread rubber in thewinding thereof on the building drum of an automotive or other tirebuilding machine, there is known the method described in Japanese PatentPublication No. 61-32980. According to this method, the length of thestrip precut to the circumferential length of the building drum ismeasured and, then, a leading portion, of predetermined length, of thestrip is taken up on the building drum at the feeding (takeup) speedequal to the peripheral speed of the drum. Then, the-feedingspeed-relative to the building drum speed is altered to either compressor stretch the strip while its intermediate portion is wound on thebuilding drum. Finally, the feeding speed is re-equalized with theperipheral speed of the building drum to wind up the remaining portionof the strip member on the drum.

[0008] However, the strip member tends to shrink with the progress oftime after cutting and the time to termination of shrinkage and theamount of shrinkage are dependent on the environment and otherconditions. Under certain conditions, the amount of post-cuttingshrinkage reaches as much as about 0.5%. Moreover, the length of thestrip member varies with the magnitude of the tension that acts on thestrip when it is transferred from a transfer conveyer to the buildingdrum and the pressure of contact between the strip and the drum. In theprior art method mentioned above, the total length of the strip memberis measured while it is undergoing shrinkage after cutting and the ratioof the feeding speed to the peripheral speed of the building drum is setaccording to the length value thus found so as to compress or stretchthe intermediate portion of the strip. As a consequence, the aforesaidratio is often irrelevant and there occurs an excess or a shortage ofcompression or stretching of the strip member, thus causing a lapping ofthe leading and trailing ends of the strip member or a gap therebetween.

[0009] Therefore, the first invention in this application provides awinding method which insures-exact abutment of said ends or abutmentwithout an appreciable overlap or gap.

[0010] Furthermore, in the process of manufacture of an automotive tire,not only the steel cord and tread rubber mentioned above but a varietyof other rubber-based strip members are cut to length and both endsthereof are joined to build single-layer or multi-layer ring orcylindrical members. For example, on the primary building machine, aninner liner (a strip member of rubber) and a plurality of ply cords(rubberized fiber cords or steel cords), all precut to thecircumferential length of the building drum, are laid up on theperipheral surface of the drum. In the secondary building machine, twosteel belts (rubberized steel cords), a cap ply (rubberized nylon cord),etc. are laid up. Some of these different strip members are not joinedby abutment at ends as described above but are joined by lapping thetrailing end over the leading end on the drum. As mentioned above, thestrip member has the property to shrink on standing after cutting tolength as mentioned above and the amount of this shrinkage varies withchanges in environment. Also as mentioned above, the length of the stripmember is altered by external forces that act on the strip when it istransferred from the conveyer to the drum. Therefore, even if the stripmember has been cut precisely to length, a variation is inevitable inthe degree of lapping of both ends. Therefore, it is common practice forthe operator to trim off the rubber or cord at the trailing end when thedegree of lapping is too large or unwind the strip partway and rewind itwith stretching when there is a gap between ends.

[0011] However, the conventional tire building machine is not equippedwith very effective means for inspecting the end joint of said stripmember and the current trend toward automation of tire building cannotcompletely avoid a risk of products with said surplus or deficiency inend lapping being shipped uncorrected and marketed.

[0012] Accordingly the second invention in this application provides atire building device which is capable of detecting a surplus ordeficiency in end lapping while a strip member is wound on a buildingdrum of said primary or second building machine.

SUMMARY OF THE INVENTION

[0013] The method for winding a strip member on a tire building machinein accordance with-the first invention in this application comprisesfeeding a strip member to a building drum by means of a transferconveyer, taking up said strip member on said building drum whilecontrolling the speeds of said transfer conveyer and building drum andjoining free ends of the strip member, which method is characterized bysetting the feeding speed of said transfer conveyer and the peripheralspeed of said building drum to equal values, taking up a leadingportion, of predetermined length, of said strip member on the buildingdrum, detecting the position of a trailing end of said strip member onsaid transfer conveyer to calculate the length of a trailing portionfollowing said leading portion of said strip member, setting the ratioof the feeding speed of said transfer conveyer to the peripheral speedof said building drum to the ratio L/Lo, where L is the length of saidtrailing portion and Lo is the residual circumferential length of saidbuilding drum, only when the L/Lo ratio is within a set range and takingup the trailing portion of said strip member, while the takeup of thetrailing portion of said strip member is stopped when the ratio L/Lodeviates out of said set range.

[0014] Thus, after completion of the takeup of a leading portion of thestrip member or just before the beginning of takeup of atrailing-portion of the strip member, the length of the trailing portionis measured and the trailing portion is wound only when the ratio L/Loof the length of the trailing portion of the strip member to theresidual circumferential length Lo of the building drum is within a setrange, with the ratio of the feeding speed to the peripheral speed ofthe building drum being set to said ratio L/Lo, with the result that theerror of length L of the trailing portion of the strip member isminimized to preclude an excessive overlap or gap between ends of thestrip member, thus leading to exact abutment of the ends or a minimum ofoverlap or gap.

[0015] The length of the leading portion of said strip member ispreferably set to 30˜80% of one circumferential length of the buildingdrum. If the set length is less than 30%, installation of a leading endsensor is difficult. Conversely if the set length is over 80%, thestretching or compression of the strip member is concentrated in thetrailing portion thereof to adversely affect the quality of the product.

[0016] The said ratio L/Lo applicable to the case of continued takeup ofthe trailing portion of the strip member is preferably set within therange of 0.9995˜1.005. Outside of this range, the amount of stretchingor compression becomes too great to insure the proper winding.

[0017] The method of winding the strip member in accordance with thesecond invention in this application comprises using a tire buildingmachine having a building drum for taking up a tire-building stripmember of predetermined length endlessly and a transfer conveyer forfeeding said strip member to said building drum, which method ischaracterized by detecting the winding-start end of said strip membertransferred from said transfer conveyer to said building drum and thewinding-finish end of said strip member with end sensors, measuring theangle through which said building drum has rotated from the output of awinding start signal to the output of a winding finish signal inresponse to output signals from said sensors by means of an angledetector, and calculate a lapping margin between the winding start endand the winding finish end of said strip member based on the rotationalangle and diameter of said building drum by means of an operationalmeals.

[0018] In the above method, since the lapping margin between the twoends of the strip member is calculated by said operational means, thebuilding operation can be continued while said lapping margin is withina preset allowable range or the operation can be discontinued or analarm be actuated when the lapping margin deviates out of said allowablerange, that is to say when the lapping margin is too large or too samll.Therefore, in the automatic building process for car tires, the risk ofproducts with lapping defects being shipped can be effectivelyprevented.

[0019] It may be so arranged that one end sensor of the above-describedtype is used to detect both the winding start and winding finish ends ofthe strip member or that two such end sensors are installed apart fromeach other by an optional angle along the circumferential direction ofthe budding drum so that one of the sensors is used to detect thewinding start end with the other sensor detecting the winding finishend.

[0020] Furthermore, a still more improved accuracy may be insured byinstalling end sensors in a plurality of positions, for example in thecenter and in positions on both sides thereof. Moreover, to cope withthe case in which one strip member has an intermediate joint of materialand this joint builds a step, it may be so arranged that the trailingend sensor is rendered operative only within a certain range, forexample in the range of 5 mm, before and after the winding start end,whereby the risk of said joint being mistaken for the winding finish endand detected as such.

[0021] In the second invention in this application, the lapping marginof-the strip member wound on the building drum includes both a positivevalue and a negative value. In other words, the case in which the twoends of the strip member actually overlap and the case in which there isa gap between the ends are included. The winding operation is stoppedwhen the actual overlap or gap is too great or too small.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a schematic view showing an example of the firstinvention in this application.

[0023]FIG. 2 is a view similar to FIG. 1, showing an example of thesecond invention in this application.

[0024]FIGS. 3 and 4 each is a schematic side view of the building drum,which explains the operation of the example shown in FIG. 2.

PREFERRED EMBODIMENTS OF THE INVENTION

[0025]FIG. 1 shows an example of the first invention in thisapplication.

[0026] As illustrated, A stands for a tire steel belt, that is to say astrip member, 1 for a transfer conveyer therefor, 2 for an end pulley, 3for a guide pulley, 4 for a drive pulley, and 5 for a building drum. Thedrive pulley 3 is connected to a drive shaft of a transfer servo motor 6and the rotation of this servo motor 6 is controlled by a transfer servoamplifier 7. The rotational speed of said transfer servo motor 6 isdetected by a pulse oscillator 8 and fed back to said servo amplifier 7.On the other hand, said building drum 5 is connected to a drive shaft ofa drum servo motor 9 and the rotation of this drum servo motor 9 iscontrolled by a servo amplifier 10. The rotational speed of said drumservo motor 9 is detected by a pulse oscillator 11 and fed back to saidservo amplifier 10.

[0027] Disposed over said building drum 5 is a leading end sensor 12 forcontactless detection of a front end Aa of said strip member A and theoutput of said leading end sensor 12 is connected to a sensor amplifier13. On the other hand, a trailing end sensor 14 for detecting theposition of the trailing end Ab of strip member A is installed over thetransfer conveyer 1. The output terminals of this trailing end sensor 14and said sensor amplifier 13 are respectively connected to a trailinglength meter 15 for calculating the length L of a trailing portion (thelength from point P to Ab) of said strip member A. When the leadingportion of strip-member A is progressively wound on the building drum 5and the leading end Aa of strip member A is detected by said leading endsensor 12, the trailing end sensor 14 detects the position of thetrailing end Ab of strip member A and said trailing length meter 15calculates the length L of the trailing portion of A which is still tobe wound on the building drum 5.

[0028] The output terminal of said trailing length meter 15 is connectedto a speed ratio calculator 16. This speed ratio calculator 16calculates the ratio L/Lo of the length L of said trailing portion tothe length of strip member A which is still to be wound on the buildingdrum 5, that is the residual circumferential length Lo (length frompoint P to Aa) and transmits a signal corresponding to this ratio tosaid transfer servo amplifier 7 and drum servo amplifier 10. Only whensaid ratio L/Lo is within a set range, the transfer conveyer 1 andbuilding drum 5 are driven at a speed ratio corresponding to the ratioL/Lo. On the other hand, when the ratio L/Lo deviates from said setrange, the transfer conveyer 1 and building drum 5 are respectivelystopped.

[0029] In winding a strip member A having a total length of 2,000 mm ona building drum having a circumferential length of 2,1000 m, the lengthof the leading portion of strip member A is set to 1,500 mm (75% of thetotal length) and the speed of the transfer conveyer 1 and theperipheral speed of the building drum 5 are set to the same value. Inthis condition, the leading portion, which is 1,500 mm long, of saidstrip member A is taken up on the drum. As the leading end Aa of thisstrip member A is detected by the leading end sensor 12, the trailingend sensor 15 is caused to detect the position of the trailing end Ab ofstrip member A and the trailing end length meter 15 to calculate thelength L of the trailing portion of the strip member A. Then, the ratioL/Lo of this length L of the trailing portion to the known residualcircumferential length Lo of the building drum 5 is calculated and whenthis ratio L/Lo is within the range of 0.995 to 1.005 (when L/Lo is −2.5mm˜0 mm), the ratio between the peripheral speed of the building drum 5and the feeding speed of the transfer conveyer 1 is set to said L/Lo sothat the strip member A is taken up under tension, i.e. under astretching force, on the building drum, whereby the leading and trailingends of the strip member A are exactly abutted against each otherwithout any surplus or deficiency. However, when the ratio L/Lo deviatesfrom the above-mentioned range, the transfer belt 1 and the buildingdrum 5 are respectively stopped and the strip member A is removed.

[0030]FIGS. 2 through 4 show an embodiment of the second invention inthis application.

[0031] Referring to FIG. 2, A stands for a strip member, 1 for atransfer conveyer, 2 for a belt pulley and 5 for a building drum. Thebuilding drum 5 and transfer conveyer 1 are driven in the direction ofthe arrowmark to wind the strip member A on the building drum 5.

[0032] Along the path in the direction of advance of said building drum5 from point P where the strip member A begins to contact the drum 5,there are provided a first end sensor 25 and a second end sensor 26.These end sensors 25 and 26 each comprises a photoelectric element whichphotoelectrically detects the end of the strip member A. Connected tosaid building drum 5 is an angle detector 30 through a toothed pulley27, a toothed belt 28 and a toothed pulley 29. The output terminals ofsaid first end sensor 25, second end sensor 26 and angle detector 30 arerespectively connected to an operational unit 31 which calculates adegree of end lapping of said strip member A.

[0033] In the above arrangement, as the building drum 5 and transferconveyer 1 are driven to take up the strip member A on the building drum5 and the leading end Aa of said strip member A reaches the position ofsaid first end sensor 25, the angle detector 30 is actuated and as thesame leading end Aa then reaches the position of said second end sensor26, the angle of rotation of said building drum 5 from the time ofdetection of the leading end Aa by the first end sensor 25 to the timeof detection of the same end Aa by said second end sensor is measured.Then, based on this measured angle of rotation, the angle θ₀ (degrees)from the second end sensor 26 to the first end sensor 25 is calculatedand stored by said operational unit 31 and, at the same time, theindicator of the angle detector 30 is reset to zero. Then, as the firstend sensor 25 detects the trailing end Ab of strip member A (FIGS. 3 and4), the building drum 5 stops rotating and the angles of rotation θ₁ andθ₂ (degrees) are measured.

[0034]FIG. 3 shows the situation where the angle of rotation θ₁(degrees) is larger than the angle θ₀ between the two end sensors 25 and26 and the end Aa and Ab of the strip member A overlap. The lappingmargin X in this situation is defined as follows.${\left( {D + {2t}} \right)\pi \quad \times \frac{\theta_{1} - \theta_{0}}{360}} = X$

[0035] where D is the diameter of the building drum 5 and t is thethickness of strip member A.

[0036] This value of X is calculated by said operational means 31.

[0037]FIG. 4 shows the situation where the angle of rotation θ₂(degrees) is smaller than the angle θ₀ between the two end sensors 25and 26 and there is a gap between the ends Aa and Ab of the strip memberA. The gap Y in this situation is given by the following equation${\left( {D + {2t}} \right)\pi \times \frac{\theta_{0} - \theta_{2}}{360}} = Y$

[0038] where D is the diameter of the building drum 5 and t is thethickness of the strip member A.

[0039] This value of Y is calculated by said operational means 31.

[0040] While the above embodiment employs two end sensors 25 and 26, thesecond end sensor 26 shown in FIG. 2 may be dispensed with and only thefirst end sensor 25 be used to determine the angle corresponding toapproximately one turn. However, when two end sensors are used in theabove embodiment, the change in length between the two sensors 25 and 26can be disregarded and a more accurate measurement can be realized. Itshould be understood that in building the second and subsequent layersof strip member A, the thickness of strip member A already taken up isadded to the diameter D of the building drum.

What is claimed is:
 1. A method for winding a strip member whichcomprises using a tire building machine having a building drum fortaking up a strip member of predetermined length without discrete-endsand a transfer conveyer for feeding said strip member to said buildingdrum, which method is characterized by detecting the winding-start endof said strip member transferred from said transfer conveyer to saidbuilding drum and the winding-finish end of said strip member by meansof end sensors, measuring the angle through which said building drum hasrotated from the output of a winding start signal to the output of awinding finish signal in response to output signals from said sensors bymeans of an angle detector, and calculating a lapping margin betweenthe, winding start end and the winding finish end of said strip memberbased on the rotational angle and diameter of said building drum bymeans of an operational means.